NATIONAL RADIO ASTRONOMY OBSERVATORY
Green Bank, West Virginia
October 1, 1993
TO: 140-ft Observers
FROM: Ronald J. Maddalena
SUBJECT: Data Archive
Traditionally, the disk drives attached to the control computer at the 140-ft
have been used to store autocorrelator and continuum data until they could be
archived to tape. During the last year we have noticed that the disk and tape
drives, because of their age and the lack of spare parts, are having more
failures and are becoming unreliable. I have recently initiated a way of
archiving data that bypasses the Modcomp disk and tape drives.
The new method of archiving involves transferring autocorrelator and continuum data, as they are taken, directly to the analysis Sun workstation where they are stored on disk. I store two identical copies of the data on different disks so that, in case a disk crashes, we will not have lost any data. About once a week, the data are copied from the Sun's disk to Exabyte tape in exactly the same tape format as we used to write with the control Modcomp. The tape is then stored as part of the permanent archive.
During three months of tests, the new archive scheme has proven to be at
least as reliable as the traditional mechanism. Furthermore, the new scheme has
many advantages over the old. For example:
If observers want, I can easily provide software that will search through the
archive data base for specific observations.
As of September 15, we have turned off the old data archive mechanism and are relying completely on the new mechanism.